Need confirmation on Overwrite and Append times for Incremental Backup

[Liam_Thompson]

Hello,

I just need someone to tell me whether my theory is right on the Incremental media set I'm creating.

I am planning to backup a server incrementally to one tape, Monday to Friday after running a weekly full backup to a separate tape on a Saturday/Sunday.

I want each incremental backup of the data to append to the one tape, so come Friday night I will have 5 incremental backups on the tape.

Come the next Monday after the weekend full backup I want the incremental backups to overwrite this tape to allow the next 5 incremental backups to sit on this tape only and so on.

I understand that the Append Period is the amount of time from when the first job is finished on the chosen media that data can be appended to that media and that the Overwrite Protection Period is the amount of time the chosen media is protected from being overwritten from the end of last job ran on the said media.....is this correct?

So my media set settings should be:

Append Period - 5 Days - which should allow append from a Monday to a Saturday???

Overwrite Protection Period - 2 Days - which should force the tape to overwrite on Monday as the last job will run on Friday???

Thanks for any insight and help

Liam Thompson

[AmolB]

Below article explains overwrite and append period in detail.

http://www.symantec.com/docs/TECH5459

[Colin_Weaver · Accepted solution]

You jobs will probably complete, but some of your understanding is wrong

The Append period starts when the media is overwritten (so the start of the Monday Backup job not the end as you wrote.) As such you could set 4.5 days (in hours), but 5 days will allow the Friday job to append to the same tape.

The Overwrite period starts at the end of the last job to write data to the media  (so the end of the Friday Backup Job) which would mean a 2 day Overwrite Protection period would result in the tape being overwritable sometime Sunday Night/Monday morning depending on how long your job takes to run on Friday. Of course the tape actually has to be in the drive/library and not the oldest tape in the media set that is overwriteable for it to actually be used as otherwise BE might choose a diffferent tape.

Also you will need a different media set for your Full backups (but I gues you knew that as you did not specify teh full retenetion in yoru question)

[Ken_Putnam]

I understand that the Append Period is the amount of time from when the first job is finished on the chosen media that data can be appended to that media and that the Overwrite Protection Period is the amount of time the chosen media is protected from being overwritten from the end of last job ran on the said media.....is this correct?

OPP is measured from the END of the last job that writes to the tape, while APP starts from the BEGINNING of the first job that overwrites the tape

You really should read through the TechNote referenced above

But specifically in your case:

For your meida set you would want an APP of 5 days and an OPP of one day

I say one day because if the Friday job ends after midnight (for whatever reasom), a two day OPP will mean that it cannot be re-used until Tuesday

[Liam_Thompson]

Thanks Colin, so I was 99% percent there at least.  Yes I have taken all the other media sets, tape loader partitions etc into account and its been basically working as expected for months now.

I needed to be sure because I originally set the append and overwrite twice as long as discussed for use with 2 sets of tapes used in a two week rotation, but my company never made these second set of tapes tape materialise haha.  So basically I've been setting all media back to scratch media at the beginning of the week to allow overwrite while waiting for these tapes to be purchased.

Thanks for your help

[Liam_Thompson]

Thanks Ken, yeah the jobs will  finish well before midnight on Friday, each job lasts approx 20 mins.